1. Field of the Invention
The invention is a method and device used in printing of images of natural, man-made materials/products, fantasy, animation, or indeed any design capable of human imagination which can be incorporated into rotogravure, digital, laser and other types of printing.
2. Background of the Invention
Printing of complex designs directly onto substrates or onto intermediate materials to be affixed to substrates can be performed by, e.g., rotogravure, digital and laser printing, wherein, often, a base coat or primer layer is applied, followed by applying the colors. These techniques allow for a substantial degree of specificity and exactness, permitting extremely complex patterns, designs and images to be reproduced from an original.
In conventional rotogravure printing, a structured roller or drum rotates through an ink bath. During rotation, the drum adsorbs the ink on the periphery of the drum, such that the ink coats, fills depressions and other structures on the surface. A doctor blade, an air blade, a manual wipe, etc. may be used to wipe excess ink off the drum. As a result, the ink is typically present only in the depressions and structures, and is not present on the curved outer surface of the drum. In a subsequent step, the drum is pressed against the printing surface, usually a paper, often by a counter roller, to transfer the ink in the depressions and structures to the paper. In transfer rotogravure printing, on the other hand, the ink is transferred from the drum to a transfer drum and then is transferred from the transfer drum to the substrate. These processes accurately recreate a first color of the pattern, design and images provided on the drum onto the paper. Conventionally, in order to add additional colors, a second drum and ink bath combination is used.
Rotogravure printing can be very inflexible with respect to creating variability due to dimensional constraints of the engraved, structured or textured drum. Examples of the inflexibility include lack of color variability and lack of dimensional flexibility, particularly in in-register designs.
In digital printing, the patterns, designs and images are provided in a digital format to the printing device. Typical digital information can be created by scanning or otherwise digitizing a natural or original image, such as a drawing or photograph. Other digital information can be created solely in a digital medium, e.g., by computer. In either case, the digital information can be manipulated to adjust any number of parameters or characteristics, such as size and color, such that the final printed image is not an exact recreation of the original. For example, should the original digitized image correspond to an area of 1 ft by 2 ft (i.e., a 1:2 length to width ratio), and the substrate has a length to width ratio of 1:4, the digitized image can be manipulated such that the digitized image fits the substrate. This can be accomplished by, e.g., cropping, zooming, non-uniform stretching, and uniform stretching.
In laser printing, a laser is aimed at a rotating polygonal mirror, which directs the laser beam through a system of lenses and mirrors onto a photoreceptor. As the beam sweeps across the photoreceptor, a stream of rasterized data held in memory turns the laser on and off to form the dots on the substrate. Lasers (now typically laser diodes) are often used because they generate a coherent beam of light for a high degree of accuracy. Where the laser beam strikes the photoreceptor, the charge is reversed, thus creating a latent electrical image on the photoreceptor surface. The surface with the latent image is then exposed to toner, i.e., fine particles of dry plastic powder mixed with carbon black or coloring agents. The charged toner particles are given a negative charge, and are electrostatically attracted to the photoreceptor where the laser wrote the latent image. Because like charges repel, the negatively charged toner will not touch the drum where light has not removed the negative charge.
The overall darkness of a laser printed image is controlled by the high voltage charge applied to the supply toner. Once the charged toner has jumped the gap to the surface of the drum, the negative charge on the toner itself repels the supply toner and prevents more toner from jumping to the drum. If the voltage is low, only a thin coal of toner is needed to stop more toner from transferring. If the voltage is high, then a thin coating on the drum is too weak to stop more toner from transferring to the drum. More supply toner will continue to jump to the drum until the charges on the drum are again high enough to repel the supply toner. At the darkest settings the supply toner voltage is high enough that it will also start coating the drum where the initial unwritten drum charge is still present, and will give the entire page a dark shadow. The photoreceptor is pressed or rolled over paper, transferring the image. Higher-end machines use a positively charged transfer roller on the back side of the paper to pull the toner from the photoreceptor to the paper. The paper passes through a fuser assembly with rollers that provide heat and pressure (up to 200 degrees Celsius), bonding the plastic toner powder to the paper.
In order to create multi-colored images with a laser printer, the different colored toners are often added by additional steps or passes, but in order to reduce misregistration between the colors, a large belt can be used to precisely add all the colors at the same time.
However, due to the nature of these and other conventional printing techniques, the produced designs, patterns and images are rigid. In other words, because conventional printing techniques reproduce the original with such a high degree of accuracy, such techniques do not allow for inherent variability in the final design.